全圆断面针梁式模板衬砌台车抗浮设计

Anti-floating Design of Needle Beam Type Formwork Lining Trolley with Full Circle Section

在全圆断面模板衬砌台车的施工应用中,混凝土浮力的设计计算是重点和难点。南水北调部分工程采用全圆断面针梁式模板衬砌台车浇筑混凝土,根据其特点,利用薄壁圆管稳定理论,对模板进行了稳定性设计及强度验算,提出对模板增加环肋后满足稳定性要求。同时,通过现场测试,提出了浮力的计算方法及混凝土粘附力概念,给出了模板衬砌台车的抗浮构造措施以及粘附系数推导公式。指出浇筑过程中,下部混凝土振捣对浮力影响很大,应采取措施减小或避免浮力作用。

It is important and difficult for design and calculation of concrete buoyancy in construction of formwork lining trolley with full circle section. Part projects of the South-to-North Water Transfer apply needle beam type formwork lining trolley with full circle section to pour. According to the trolley＇ s characteristics, the stability design and strength checking are carried out by using stable theory of thin circular tube, which indicate that adding ring stiffened for formwork can meet stability requirement. Furthermore, through on-site measurement, the calculation method of buoyancy and adhesion concept of concrete are put forward, and the structural anti-floating method for formwork lining trolley and derivation formulas for adhesion coefficient are indicated. Through analysis, it is pointed out that during pouring, lower concrete vibrating has important effect on buoyancy, and measures which can reduce buoyancy should be applied.